Door latches of various types are well known. Door latches, or catches, serve to hold a door in place when it is closed, even if the door is not locked. Such latches have been used in conjunction with many different types of doors, including primary doors and secondary doors such as screen doors.
The present invention is directed to an improved locking apparatus suitable for doors of any type, but is particularly directed to secondary doors such as screen doors commonly found on residential dwellings.
Actually, a door latch functions to latch or interconnect two door portions which are otherwise relatively movable. The first door portion might be the door itself while the door frame might be the second door portion. Of course, the phrase "first door portion" could also be applied to the frame and the phrase "second door portion" applied to the door.
In order to latch two door portions together, normally a latching apparatus is located on one door portion and a strike is located on the other. The latching apparatus normally includes a movable latching element, such as a "nose" or "bolt," which is suitable for engaging the strike. Typically, a handle, e.g., a knob or lever, is attached to the movable latching element for ease of use.
The strike which engages the movable latching element could be a simply L-shaped bracket or a spring-loaded bar; alternatively, the door frame itself can function as the strike, the latching element engaging the frame, in which case the frame simply has a "strike area" which does not include a specially designed strike.
It should be stressed that the latching apparatus including the movable latching element could be mounted on the door frame while the strike is located on the door, although this is not the normal latching scheme. It should also be noted that the frame of a secondary door may in fact be formed partially or completely by the frame of the associated primary door.
As noted above, the latching apparatus of the present invention is particularly directed, though not limited, to a secondary door such as a screen door for a dwelling. Thus, the present discussion focuses on screen door latches for purposes of illustration, but the scope of the invention is not so focused.
Although prior art screen door latches are well known and generally function adequately for their intended purposes, several problems remain. Some problems stem from the fact that screen doors are used in conjunction with primary doors to seal an opening in the wall of a dwelling. Typically, the screen door is emplaced after the primary door is hung. Thus, the screen door and its frame and latching apparatus must adapt to mechanical constraints associated with the primary door's frame.
More specifically, assuming that the latching apparatus is attached to the screen door and the strike is attached to the screen door's frame, oftentimes the door frame is such that the strike does not extend sufficiently toward the latching apparatus to conveniently allow for engagement of the movable latching element and the strike. Thus, with prior art latching apparatus, the strike usually must be shimmed or the latching apparatus has to be relocated, or both, in order to provide for latching and unlatching of the screen door.
The unadjustability of prior art latching apparatus also creates other problems as well. For example, if the strike is shimmed, it may excessively extend into the doorway, thus creating a nuisance if not a hazard. In addition, it is quite possible that the strike can extend too far even without having been shimmed. In this case, since the prior art locking apparatus cannot be adjusted, the entire latch apparatus (not including the strike) has to be relocated closer to the center line of the door to accommodate the strike.
Similarly, the backset of a latching apparatus might have to be located in a particular position with respect to the edge of the screen door. This would be desirable if it is desirable to vertically align the latching apparatus with an auxiliary piece of hardware such as a deadbolt lock; or, a particular backset might be needed simply to vertically center the latching apparatus in the longitudinal frame piece of the screen door for esthetic reasons.
In such instances, when using prior art latch apparatus, the strike typically has to be shimmed out to engage the movable bolt or nose of the latch apparatus. If the latch apparatus has a particularly long "throw" this shimming process might be unnecessary, but such lock apparatus are typically very cumbersome and complicated.
The unadjustability of prior art latch apparatus becomes particularly troublesome in light of the fact that screen doors, and particularly metal and plastic screen doors, experience thermal expansion and contraction which can fairly significantly change the amount of clearance or interference between the latching apparatus mounted on the door and the strike area or strike located on the door frame. In fact, it might be necessary to shim the strike or relocate the latching apparatus to account for thermal effects.
Prior art screen door latches, in addition to not being adjustable, suffer from another inadequacy. Most prior art door latches include two handles, one handle being located proximate to each surface of the door, i.e., the inner surface and the outer surface. Typically, the latch apparatus includes a lock which is in the nature of a small tab or button which can be slid or rotated to lock the latch thereby preventing unlatching of the door. However, such latching apparatus do not allow for "panic unlatching" of the door wherein the door can be opened simply by engaging the latch handle proximate the inner surface of the door. Absent means for panic unlatching, the individual seeking to exit the door must locate the locking tab and move it appropriately. Since there are no standards or accepted methods for locking such latching apparatus, the individual generally must experiment with the locking apparatus to determine the proper direction for unlocking, unless of course the individual is quite familiar with the particular latching apparatus with which he is dealing.
Lack of a "panic unlatching" means particularly causes problems in panic situations such as when the individual is fleeing a fire or when the individual needs to leave the dwelling rapidly and the doorway is not sufficiently lighted.
In addition to the problems associated with unadjustability and the inability to readily unlatch in a panic situation, prior art latching apparatus do not readily accommodate, without modification, various types of outside door handles. That is, prior art latching apparatus are typically designed to accept only a rotating spindle which is attched to a door knob or handle connected to the outside surface of the door; or the prior art lock apparatus is designed to accommodate only a spindle which moves axially when driven by a push button located on the outside surface of the door. Thus, the lock apparatus manufacturer must supply two types of latch apparatus if he wants to market his product for rotating and push button handles. This means that the manufacturer must assemble and stock two sets of components and is not able to capitalize on all of the potentially available economies of scale.
The present invention is directed to the problems associated with the prior art door latching apparatus. Specifically, the locking apparatus of the present invention is adjustable to accommodate various types and configurations of strikes; it allows for panic unlatching or unlocking of the latch apparatus; and/or it accommodates rotating outside handles and outside handles which apply an axial force on the latch's spindle.